Method for verifying the authenticity of documents

ABSTRACT

The invention relates to a method for testing the authenticity of documents, in particular bank notes, documents of value or security documents, by authenticity criteria. To increase the reliability of authenticity testing of documents, at least two different authenticity classes each with one or more authenticity criteria are provided, the individual authenticity classes differing in at least one authenticity criterion. An authenticity class is selected from the different authenticity classes and the document tested by the authenticity criteria of the selected authenticity class. The document is assigned the selected authenticity class if the document meets the authenticity criteria thereof. This obtains higher reliability of authenticity testing since this method makes it possible to determine those documents that meet higher authenticity requirements, i.e. stricter authenticity criteria, than the other documents and are therefore authentic with higher probability.

FIELD OF THE INVENTION

This invention relates to methods and apparatuses for testing the authenticity of documents, in particular bank notes, documents of value or security documents, according to the generic part of the independent claims.

BACKGROUND

Authenticity testing of documents is generally done by measuring certain authenticity features, for example optical, electric or magnetic features, on a document under test and then testing the measured authenticity features with reference to given authenticity criteria. For example, the optical reflection behavior of the document is measured as an authenticity feature and it is then tested whether the measured reflection behavior undershoots or exceeds a certain threshold value as the associated authenticity criterion. Depending on the test result the document is classified as authentic or false.

The reliability of detecting forgeries can be increased for instance by tightening the authenticity criteria in the testing of certain authenticity features, for example by raising or lowering threshold values. In practice the authenticity criteria cannot be tightened at will, however, since this would make the proportion of authentic documents not recognized as authentic—and possibly rejected or misclassified—too high.

In bank note processing machines that are used in particular in commercial banks for deposit testing and clearing, this would lead for example to elevated effort for postprocessing bank notes not recognized as authentic by hand and possibly further by machine.

In authenticity testing in money-depositing machines, a general tightening of authenticity criteria would mean that in particular used or soiled authentic bank notes, whose authenticity features are less distinct due to soiling or damage compared to freshly printed bank notes, are not recognized as authentic and consequently rejected or withheld as alleged forgeries, depending on the case of application.

The reliability in recognizing counterfeit bank notes is therefore limited by the required low proportion of authentic bank notes not recognized as authentic. This is problematic especially when forgeries are not recognized as such due to “loose” authenticity criteria and return to circulation, for example after one customer deposits counterfeit bank notes in self-service recycling machines and the bank notes not identified as forgeries are then issued to other customers.

The method known from DE 196 18 541 A1 relates to determining a sorting class from a number of bank note properties, such as denomination, security features and soiling. Measuring results for the bank note properties are first mapped onto discrete classes and combined in a class vector. The class vector is finally compared with individual rule vectors each corresponding to a certain sorting class. If the class vector of the bank note matches a rule vector, the bank note is assigned the sorting class corresponding to the particular rule vector. This method permits sorting classes to be determined fast and precisely. However, the derivation of a class for individual security features, i.e. the actual authenticity testing, is done by methods known from the prior art, so that the above-described problems also arise here when for example a raising or lowering of threshold values for authenticity features is intended to increase or reduce the reliability in authenticity testing.

EP 0 101 115 A1 discloses a device for recognizing bank notes wherein a digital picture of the bank note is taken and compared with a previously stored reference picture of a reference bank note. If a first comparison, in particular on one half of the bank note, does not yield a sufficiently reliable result, the comparison can be repeated in other areas of the bank note, for example with other comparative values. However, this opens up the possibility of selectively soiling or damaging security-relevant areas of a counterfeit bank note to effect a test of other areas with possibly more easily imitated security features and thus—falsely—a positive test result.

SUMMARY

It is the problem of the present invention to state methods and apparatuses for authenticity testing that permit documents to be tested with elevated reliability, in particular without simultaneously increasing the proportion of authentic documents falsely not recognized as authentic.

This problem is solved by the authenticity testing methods and by the corresponding authenticity testing apparatuses according to various aspects of the invention.

In the authenticity testing method according to one aspect of the present invention, at least two different authenticity classes each with one or more authenticity criteria are provided, for individual authenticity classes differing in at least one authenticity criterion. For authenticity testing, an authenticity class is selected from the different authenticity classes and the document tested by the authenticity of criteria of the selected authenticity class. The document is assigned the selected authenticity class if the document meets its authenticity criteria. The authenticity criteria are for example threshold values or intervals for the authenticity features used for testing. Authenticity features to be used are for example optical, magnetic, electric or physical features, e.g. optical reflection, transmission or emission, magnetic permeability, electric conductivity, dielectric constant, thickness and format of the document as well as watermarks.

The invention is based on the idea of combining different authenticity criteria in authenticity testing of documents into a plurality of authenticity classes, the requirements for authenticity varying in strictness depending on the authenticity class, since each authenticity class generally includes a different number of authenticity criteria and/or authenticity criteria varying in strictness. If the authenticity class selected has for example high requirements for authenticity, e.g. very high threshold values for optical reflection or transmission, the authenticity of documents meeting the authenticity criteria of this selected authenticity class can be affirmed with high probability. Documents not meeting the authenticity criteria of a selected authenticity class can be tested by other selected authenticity classes with lower requirements for authenticity, for example lower threshold values, so that their authenticity can be affirmed with accordingly lower probability. Altogether, this results in a division of the authenticity property, i.e. the measured authenticity features, of the documents under test into different authenticity classes. This differentiation of the result of authenticity testing makes it possible to determine those documents that are authentic with higher probability than in prior art authenticity testing methods, thereby altogether increasing the reliability of determining authenticity. Simultaneously, the other documents can still be tested by the hitherto usual—generally “less strict”—authenticity criteria, thereby keeping the proportion of authentic documents not recognized as authentic low.

In a development of the method, it is provided that the fitness and/or denomination of the document is determined and the authenticity class then selected in dependence on the fitness and/or denomination of the document. Denomination is the value or currency of the document under test. Fitness of the document is generally given by fitness features such as degree of soiling, limpness, damage, such as tears, holes or faulty places in the printed image, and foreign bodies, such as adhesive tape. For example, the authenticity class can be selected in the authenticity testing of a document in dependence on the degree of soiling of the document, whereby clean and undamaged documents can be tested by much stricter authenticity criteria, e.g. higher threshold values, than very soiled or damaged documents. This clearly increases the reliability of recognizing forgeries in clean or slightly soiled documents. Altogether, this fitness-dependent authenticity testing permits documents with high fitness to be identified as authentic or false with high reliability. Since only the testing of documents with high fitness is tightened, the proportion of authentic documents not recognized as authentic simultaneously remains low.

According to a further aspect of the invention, a portion of the authenticity criteria used for testing authenticity is determined on counterfeit documents. This extends authenticity testing with defined authenticity criteria by additional authenticity testing with additional authenticity criteria, the additional authenticity criteria being determined on counterfeit documents The additional authenticity criteria are generally determined in a separate method, e.g. in specially provided devices, wherein counterfeit documents are tested in particular for characteristic differences over authentic documents. Additional authenticity criteria are determined from the found differences and then supplied to the authenticity testing method. Documents are still tested hereby fixed authenticity criteria and classified as authentic if they meet the authenticity criteria. In addition, forgeries can be recognized if the tested documents do not met the additional authenticity criteria determined on known forgeries, said criteria preferably relating to characteristic differences between a found forgery and authentic documents. This achieves elevated reliability in the recognition of forgeries, in particular with respect to known forgeries that are in circulation.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in more detail with reference to examples shown in figures, in which

FIG. 1 shows the schematic structure of an apparatus for inventive authenticity testing of documents;

FIG. 2 shows the schematic structure of an authenticity testing system using authenticity criteria determined on counterfeit documents, and

FIG. 3 shows the schematic structure of a system for processing deposited bank notes.

DETAILED DESCRIPTION

FIG. 1 shows the schematic structure of an apparatus for inventive authenticity testing of documents. Documents 10, for example bank notes, provided in input device 11 are removed singly from input device 11 and transported with the aid of transport system 14 to output device 12. Here documents 10 are sorted into three different sorting classes and outputted into corresponding output pockets 13. On the way between input device 11 and output device 12 document 10 under test is transported past measuring device 15. Measuring device 15 measures the authenticity features of document 10 under test. It optionally also measures fitness features characterizing the fitness of document 10. The dashed line in measuring device 15 is intended to indicate that measuring device 15 can have two or optionally more components for separately measuring authenticity and possibly fitness features. It is fundamentally also possible, however, to measure both authenticity and fitness features together in one measuring device. In the shown example, measuring device 15 only measures on one side of document 10 under test. However, the apparatus can generally also be designed so as to measure document 10 from both sides, e.g. by two opposing measuring devices 15 through which document 10 is transported.

Information about the features measured in measuring device 15 is transferred to evaluation device 16 where inventive authenticity testing is done. Selection of a certain authenticity class and its assignment to document 10 under test are preferably realized by a computer program. The computer program tests for example whether an authenticity feature, e.g. optical reflection, measured on document 10 under test is greater than a threshold value for optical reflection belonging to the certain authenticity class. If the test result is positive, document 10 is assigned the certain authenticity class, e.g. by writing a number characterizing the authenticity class into a variable characterizing the authenticity of document 10. If the test result is negative, the computer program continues testing the measured authenticity feature by lower threshold values belonging to other authenticity classes, i.e. less strict authenticity criteria, and assigns document 10 a corresponding authenticity class. Altogether, this results in a division of the authenticity property, i.e. the measured authenticity features, of documents 10 under test into different authenticity classes. If all these tests deliver a negative test result, document 10 is classified as false.

In a preferred development of the method, the fitness of document 10 is additionally determined from the measured fitness features. Document 10 is then assigned one of several fitness classes characteristic of the particular fitness of the document under test. Bank note testing usually involves three fitness classes, namely unfit, fit and ATM-fit (very fit). The authenticity class is then selected in subsequent authenticity testing in dependence on the fitness class assigned to document 10 under test. ATM-fit bank notes are preferably subjected to very strict authenticity criteria, while unfit or fit bank notes have to meet less strict authenticity criteria of other authenticity classes to still be classified as authentic. To increase the reliability of authenticity testing, it is also possible to do an additional authenticity test on documents 10 of a certain fitness class, for example fit or ATM-fit bank notes. Such an additional authenticity test can be done for example on the basis of already measured data for individual authenticity features.

Denomination can fundamentally likewise be determined via measuring device 15 and evaluation device 16, but this might also be done in separate measuring and evaluation devices.

In a typical sorting mode, for example for use in a bank note processing machine for deposit testing and clearing, documents 10 are divided into one or more sorting classes and outputted into corresponding output pockets 13. Output device 12 is driven by evaluation device 16 such that a first one of output pockets 13 receives bank notes—optionally of only one desired denomination—that are ATM-fit, were assigned an authenticity class with high requirements for authenticity, i.e. strict authenticity criteria, and are in a desired position, i.e. a certain printed pattern is visible from above and optionally aligned in a certain way. A second output pocket, the so-called reject pocket, receives those bank notes that could not be assigned an authenticity class and/or are not in a desired position and/or optionally do not belong to the desired denomination. This output pocket optionally also receives faultily drawn-in and/or transported bank notes, e.g. double picks or folded bills. Finally, a third output pocket receives all other bank notes, i.e. fit, unfit and ones that were assigned an authenticity class with lower requirements for authenticity, i.e. less strict authenticity criteria. If for example a stack of bank notes of a certain denomination is inputted in a mixed position, this sorting mode permits those bank notes of a certain denomination to be sorted out that are authentic with high probability, ATM-fit and simultaneously have a desired position. Bank notes that meet these criteria can then be provided for immediate further output, e.g. in a self-service recycling machine.

FIG. 2 shows the schematic structure of an authenticity testing system using authenticity criteria determined on counterfeit documents. The mode of functioning of such a system differs from the example shown in FIG. 1 mainly in that the authenticity test done in evaluation device 16 is performed in two steps. In a first step, the authenticity test is done using authenticity criteria, which are preferably divided into authenticity classes. The authenticity class can be selected in dependence on the determined fitness of document 10 under test, as explained above in connection with FIG. 1. If the measured authenticity features meet the given authenticity criteria, document 10 is assigned the corresponding authenticity class. In a second step of the authenticity test, an additional test is done using authenticity criteria determined on known counterfeit documents. Said authenticity criteria are determined in bank note testing machines suitable for this purpose, e.g. in a central bank or at a corresponding service provider. For reasons of data reduction there are preferably authenticity criteria that are characteristic of the difference between a counterfeit and an authentic document. The authenticity criteria used in the second step of the authenticity test are transferred in the shown example from control device 31, e.g. a server of a central bank or central service provider, over wire-bound or wireless connection 32 to one or more test stations 30 simultaneously. The corresponding data can also be transferred by means of suitable data carriers, e.g. flash card, memory chips, floppy, CD or DVD. If a corresponding characteristic difference is now ascertained in the second step of the authenticity test, document 10 can be identified as a forgery with high probability even if it meets the authenticity criteria in the first step of the authenticity test. The chronological order of the two steps can fundamentally be selected at will.

Altogether, this system permits simple and fast updating of features and criteria for testing the authenticity of bank notes in any number of test stations 30 simultaneously, thereby guaranteeing high reliability in the recognition of counterfeit bank notes that are in circulation.

FIG. 3 shows the schematic structure of a system for applying the inventive authenticity testing. Documents 10, bank notes in this example, are deposited at commercial bank 39 by a depositor. The deposit can be made e.g. at the terminal of a self-service recycling machine. In test station 30, which can be part of the terminal, the bank notes are tested for authenticity. If the bank notes meet the very strict authenticity criteria of a selected authenticity class, they can be provided for immediate further output, for example at the same terminal, other output terminals 34 and/or bank teller window 36. All bank notes that do not meet these very strict authenticity criteria are supplied to central testing device 35, for example in central bank 40, to be subjected to further authenticity testing, this testing also using so-called high-security features that guarantee especially reliable recognition of counterfeit bank notes. Bank notes that meet these criteria can now be put back into circulation by being returned to commercial bank 39 to be paid out at output terminals 34 or bank teller window 36.

This example furthermore includes controller 31 in which counterfeit bank notes are used to determine additional authenticity criteria—as stated above in the description for FIG. 2—that relate to characteristic differences between authentic bank notes and bank notes recognized as forgeries in central testing device 35. The forgeries can be transferred directly from testing device 35 to controller 31. The authenticity criteria determined there are then transferred over connection 32 to test station 30 and can be used there—optionally in addition to the authenticity criteria divided into different authenticity classes —for testing the authenticity of bank notes.

To permit deposited forgeries to be retraced, characteristic data of the deposited bank notes, e.g. printed images and/or serial numbers, can in addition be stored in control device 31 together with data on the depositor, e.g. account number and/or personal identification number (PIN). If a bank note is recognized as a forgery in central testing device 35, characteristic data of the bank note, e.g. printed images and/or serial numbers, are transferred to control device 31. There, comparison of the stored data with the transferred data permits the depositor of the counterfeit bank note to be identified. Controller 31 can either be installed inside commercial bank 39, as shown, or be located outside the same, for example at a central service provider.

The system shown in FIG. 3 deals by way of example with the application of the inventive method for testing the authenticity of bank notes in a depositing machine at a commercial bank. However, the authenticity testing can fundamentally also be done in a bank note processing machine in which bank notes are inputted by an employee for testing and/or sorting, e.g. after being deposited at the teller window of a commercial bank. The authenticity testing and the subsequent course of the method involving sorting, reissue and/or transfer for testing in a central bank are analogous. 

1. A method for testing the authenticity of documents wherein a document is tested by authenticity criteria, comprising providing at least two different authenticity classes each with one or more authenticity criteria for a valid document, the individual authenticity classes differing in at least one authenticity criterion, so that requirements for authenticity vary in strictness depending on the authenticity class, determining fitness or denomination of the documents; selecting an authenticity class from the different authenticity classes in dependence on the determined fitness or denomination of the document, testing the document by the authenticity criteria of the selected authenticity class, and assigning the document the selected authenticity class if the document meets the authenticity criteria thereof; wherein if the authenticity criteria of the selected authenticity class are not met, a further authenticity class with lower requirements for authenticity is selected and the authenticity testing repeated by the authenticity criteria of the selected further authenticity class.
 2. The method according to claim 1, wherein the fitness of the document is dividable into fitness classes, the document is assigned a fitness class corresponding to the fitness and the authenticity class for testing the authenticity of the document is selected in dependence on the fitness class assigned to the document.
 3. The method according to claim 1, wherein individual documents are sorted in accordance with the particular assigned authenticity class.
 4. The method according to claim 3, wherein the individual documents are sorted additionally in accordance with one or more characteristics selected from the group consisting of fitness, fitness class, and denomination of said individual documents.
 5. The method according to claim 3, wherein the individual documents are sorted and thereby divided into one or more sorting classes, a first sorting class receiving the documents that have high fitness (ATM-fit), were assigned a certain authenticity class and are in a desired position and/or belong to a desired denomination.
 6. The method according to claim 5, wherein a second sorting class receives the documents that are not assigned any of the authenticity classes, are not in the desired position, or do not belong to a desired denomination.
 7. The method according to claim 6, wherein a third sorting class receives all other documents not divided into the first or second sorting class.
 8. The method according to claim 5, wherein the documents divided into the first sorting class are provided for a further immediate use.
 9. The method according to claim 7, wherein the documents divided into the third sorting class are transferred to a testing device and subjected there to further authenticity testing, in particular using further authenticity criteria.
 10. The method according to claim 9, wherein those of the documents tested in the central testing device that are fit or ATM-fit and meet the authenticity criteria of authenticity testing in the central testing unit are provided for a further use.
 11. The method according to claim 1, wherein the documents are inputted by a depositor and supplied to authenticity testing, and data identifying the depositor and characteristic data of the inputted documents are stored together.
 12. The method according to claim 1, further comprising testing counterfeit documents for characteristic differences over authentic documents; wherein at least a portion of the authenticity criteria used for authenticity testing is determined from said characteristic differences.
 13. The method according to claim 12, wherein the authenticity testing is performed in a test station and at least one portion of the authenticity criteria used for authenticity testing in the test station is determined in a control device on the basis of counterfeit documents.
 14. The method according to claim 13, wherein information about the authenticity criteria determined on the basis of counterfeit documents is transferred from the control device to the test station.
 15. The method according to claim 14, wherein the information transferred from the control device to the test station relates to characteristic differences between a counterfeit and an authentic document.
 16. An apparatus for testing the authenticity of documents, comprising at least one measuring device for measuring at least one authenticity feature on a document under test, wherein the measuring device is formed for measuring at least one fitness feature that characterizes the fitness of a document under test, and at least one evaluation device for testing the measured authenticity feature by authenticity criteria, wherein the evaluation device is formed for testing the authenticity of the document by authenticity criteria of an authenticity class selected from a plurality of different authenticity classes, wherein the evaluation device is formed for determining the fitness of the document from the measured fitness feature and for selecting the authenticity class in dependence on the determined fitness of the document; and wherein the authenticity classes each include one or more authenticity criteria for a valid document and differ in at least one authenticity criterion, so that requirements for authenticity vary in strictness depending on the authenticity class, and the document is assigned the selected authenticity class if the document meets the authenticity criteria thereof, and if the document does not meet the authenticity criteria of the selected authenticity class, a further authenticity class with lower requirements for authenticity is selected for further testing the authenticity of the document by the authenticity criteria of the selected further authenticity class.
 17. The apparatus according to claim 16, wherein an output device is provided for outputting documents sorted according to authenticity class and/or fitness and/or denomination.
 18. The apparatus according to claim 16, wherein the evaluation device is formed for testing the authenticity of the document by authenticity criteria determined from characteristic differences of counterfeit documents over authentic documents.
 19. The apparatus according to claim 18, including a control device that is formed for determining the authenticity criteria on counterfeit documents and from which information on the authenticity criteria determined on the basis of counterfeit documents is transferable to the evaluation device.
 20. A method for testing the authenticity of documents wherein a document is tested by authenticity criteria, comprising the steps of: providing at least two different authenticity classes each with one or more authenticity criteria, the individual authenticity classes differing in at least one authenticity criterion, so that requirements for authenticity vary in strictness depending on the authenticity class, determining a fitness of the document; selecting an authenticity class from the different authenticity classes based on the fitness of the document, and testing the document by the authenticity criteria of the selected authenticity class, and assigning the document the selected authenticity class if the document meets the authenticity criteria thereof.
 21. An apparatus for testing the authenticity of documents, comprising at least one measuring device for measuring at least one authenticity feature on a document under test, and at least one evaluation device for testing the measured authenticity feature by authenticity criteria, wherein the evaluation device is formed for testing the authenticity of the document by authenticity criteria of an authenticity class selected from a plurality of different authenticity classes, wherein the authenticity classes each include one or more authenticity criteria and differ in at least one authenticity criterion, so that requirements for authenticity vary in strictness depending on the authenticity class, and the document is assigned the selected authenticity class if the document meets the authenticity criteria thereof; and wherein the measuring device is formed for measuring at least one fitness feature that characterizes the fitness of a document under test, and the evaluation device is formed for determining the fitness of the document from the measured fitness feature and for selecting the authenticity class in dependence on the determined fitness of the document. 